The present invention relates to a micromechanically producible capacitive pressure sensor.
A closed chamber at a reference pressure is sealed by an elastic diaphragm which is exposed to an external pressure. The electrically conductive diaphragm forms a plate capacitor with the opposite side of this chamber. The diaphragm is deformed because of the pressure difference between the external pressure and the internal reference pressure. The capacitance of this capacitor changes owing to the change in the distance between the diaphragm and the rear side of the chamber, which acts as a counter-electrode. The external pressure can be determined from this change in capacitance.
U.S. Pat. No. 5,095,401 by Paul M. Zavracky et al., describes pressure sensors on an SOI substrate, in which a hollow is produced by removing a region, made from silicon oxide and produced by means of LOCOS, through small openings in a layer applied thereupon. These openings are subsequently sealed by oxidizing the adjoining silicon or by applying a further layer made from silicon nitride, polysilicon or the like. This patent specification also describes the use of the method of production specified there for producing pressure sensors which measure in a capacitive fashion. A constituent of the diaphragm of this pressure sensor is a crystallized silicon layer which is used outside the pressure sensor to integrate electronic components, and is used in the region of the diaphragm to form piezoelectric resistors.